Flux for treating aluminum and aluminum alloys



Patented Oct. 6, 1953 FLUX FOR TREATING ALUMINUM AND ALUMINUM ALLOYS James A. Davis, Columbus, and La Verne W. Eastwood, Westerville, Ohio, assignors, by mesne assignments, to The Pennsylvania Salt Manufacturing Company No Drawing. Application April 1, 1950, Serial No. 153,486

Claims.

This invention relates to the modification or aluminum or aluminum base alloys and more particularly to a flux composition and method of treatin aluminum or aluminum base alloys to improve their physical characteristics.

Aluminum and aluminum base metals in general when cast without prior special treatment are found to have poor grain structure, small pinholes dispersed throughout the metal, poor tensile strength, and to be difficult to work or machine. Also, where the aluminum or aluminum base metal has an appreciable silicon content, poor modification of the silicon in the final casting is observed.

These undesirable characteristics tend to Weaken the final metal with respect to its mechanical properties, interfere with later working or machining of the aluminum or aluminum base alloy and, where a fine finish is desired, detract from the appearance of the final finished article, the pinholes producing a dull unattractive porous surface. This results in castings unsuitable for many purposes, e. g. pressure cookers, pistons, household fixtures, etc., thus limiting the useful range of the final cast metal.

Various processes of metal treatment and various treating materials have heretofore been resorted to in order to improve the aluminum or aluminum base alloys in attempts to eliminate or substantially decrease the heretofore mentioned undesirable characteristics found in the final metal castings. However, as far as We are aware, there has been no single process or fluxing material developed, prior to our invention, which will improve the final metal casting obtained with respect to grain structure, pinhole porosity, tensile strength and improved silicon modification. The aluminum treating processes and compositions heretofore used, though frequently giving excellent results with respect to improving the final aluminum casting or sheet metal as to one or maybe two of these characteristics would not benefit the metal treated with respect to the other undesirable characteristics, and would in some instances aggravate these other undesirable characteristics. This is particularly true with respect to grain refiners in general and to silicon modifiers such as sodium metal, their use tending to increase the pinhole porosity of the final cast metal. In addition, the use of sodium metal is hazardous, While the use of a grain refiner such as metallic boron involves an expensive smelting operation. It has, therefore, been necessary, when using prior known treating methods and compositions, to

2 subject the aluminum being treated to several separate treatments each adapted to improve the final cast metal with respect to a difierent characteristic.

Among prior materials used for treating aluminum melts can be mentioned boron, titanium, sodium and various gaseous agents including fiuorine compounds, these being added to the molten aluminum prior to final casting. Elements such as boron, titanium and sodium were added both in their elemental form and as chemically combined with other elements, the boron and titanium being added mainly for the purpose of improving the grain structure oi. the final casting, whereas the sodium was found to improve the silicon modification. Gases were generally bubbled through the molten aluminum to help decrease the formation of pinholes in the final casting.

In order to obtain a multiple fiuxing action, fiuxing ingredients have heretofore been used combining several of the above-mentioned elements into a single fiux composition. For example, sodium fiuoborate has heretofore been used singly as a fiuxing material. However, it has been noted that where such fiuxing material has been used alone wholly satisfactory results have not been obtained. Sodium fiuoborate, when used alone as a flux material, though tending to improve the physical characteristics of the final castings, is objectionable due to the large amount of dross formed during the fiuxing operation. The amount of dross formation is such as to make its use in regular foundry practice substantially prohibitive due to the large amount of metal lost in the dross when the sodium fiuoborate is used.

It may be possible to reduce the amount of dross formed by using the sodium fiuoborate in smaller amounts and maintaining the temperature of the aluminum or aluminum base metal melt below about 1400 F. However, such operation would be unsatisfactory since it is generally desirable to have a fiuX which will operate successfully at melt temperatures of about 1400" F.

' to 1450" F., this being the usual maximum temperature range employed prior to casting.

When attempts were made by us to use sodium fiuotitanate alone as a fluxing material for aluminum an increase in pinhole porosity was noted even though the grain refinement and silicon dispersion were at first somewhat improved. The grain refinement obtained, however, apparently was not permanent since the size of the resulting aluminum castings, when the aluminum was treated in accordancewith our;present invention,

strength. In addition, the tensile properties of heat-treatable alloys were by the use of the fluxes but were actually improved. The amount of improvement, obtained with respect to any of the above characteristics dep n ed somew at. s eulsi expe ted, on the qualityf the me t; being t seei'edL Iiwee else notedz h l e m.e zei ne he finelr in was improved by the use of these two materials towh rethe er u d. R at In practicing our invention the flux compositogether the alkali flupborate and alkali fluoiten te. a t Ob ain eilhei n l y gen 7 her the. ll? s. epa e br eiee t e sed ll? is preferably p u e l nie me e uminemee einei e u .1%". as 9 on a n 1. 1 .3 l fi i y of h flex n m te i e eemele e container wi h ed.-. he eeeteinere. ma be sealed so 1$. prevent. 119 x; eeem e contaminated, particularly with moisture, prior to use. Hows ince'the flux composition shows substantially no tendency to absorb moisture from the air. When the flux composition is prepared by sintering, the sintered material is crushed or ground to the containers from which measured amounts are used asfln'eeded. Where it is desired to have a able to use the fluxing material in the form of the fused sticks. However where a more rapidfluxto be preferred. The rate of flux-ingaction is controlled" primarily by the size towhioh the Satisfactory fluxes may-be prepared by using the alkali fiuoborate. and. alkali fluotitanate. in

fluxing agents added thereto, the final fluxcornposition depending on the particular type ofalumetalpalloyto be modified. In practice, wehave eun e t, e erable in eeth as. a a n t e mprov ment btain d tion is. preferably prepared by fusing or sintering Ql mo s urere lfls ei r el x eing inserted into themetal melt when the fiu ver i v e a tion. is n t. b olute necessary desiredpart icle size and then place'd insuitable slowfiuxing treatment, it has been found prefer mg action is required flux materialis reduced in the grinding'process.

varying portions with or withoutother beneficial minum: e e ee min preparing flux compositions; in accordance with our invention, to use frames, to 75% of sodium fiuoborate and 25 to 75% of sodium fluotitanate. the minimum amounts are used, the beneficial results obtainedby using these materials in combination in a fiuxing composition isreduced. If more than the upper limitsgiven are used, there is a tendency for the flux composition to show someof; the undesirable efiec'ts, previouslynoted as being; observed where the alkali fluoborate or the, alkali fluotitanatewere, used alone. Inorder t better illustrate o ur invention thelfollowjin'g examples of sojrn e fiux compositions. are given. These compositions have been successfully "used silicon; modifi-.

were found to beparticularly improved; with respect to grain refinement and tensile not adversely affectedthe g-round'sinteredflux r. u num.

Where less than I no objectionable; I

in treating various types of aluminum and al'u minum metal alloys.

Example 1 p 7 Percent Sodium fluoborate 50 Sodium fluotitanate 50 Example 2 Sodium, fluoborate 30 Sodium fluotitanate t 30 Calcium fluoride 6' Sodium chloride 34 Example 3 so um fleeleere 30 Sod i um fluotitanate 30 Sodium chloride 16 *Gryolite l6 Ezrample 4 Sodium. fluohorate 30 Sodium fluotitanate 39 Sodium: chloride 2 Sodium, fluoride 11 Ewmp sed um, fluebor te-fi- -a .5 Po a sium; fluet enete e-Te: r? fi 15 Example 6 Potassiumfluoborate 50 Sodium fiuotitanate. 50

hefi xeeineeeh-ef. eahe eeexe leezw pr pare by usin o e her h in redie ts. listed. n. sin flux om o itions. o out vention, etieieete esultsheve be n bta ned enx as eent yv tirr ne he:

melt s;- he; ee n etien akesplae e ee apid tir in he ldnreiere ly e. avoided ineei ill-t em nstan e e.tullye n reeeel he i ne erpree ty oti eifine a n arti ul rl-rh reia h hl efined elueate i.

end he fleree'ef ur. nv n n o be more. suitably adapted to the. treatment of what is commonly knownin the trade .as secondrrm el. ev r thej n ien s m way lirn'itedtosuch treatment, the be'neficialresults d iir. fl treeimentbeine. de ned W thmest el m m jmt r. el minumh se metals, the de re of refinement observed depending somewhat uponth'e conditions orthe aluminum before treatment. In describing our invention several special flux formulations have been given; These id mulationsare givenby Way of illu stration-only in order. to b etter describe the invention and should notbe considered in any way as limiting the scope oj -the jinvention thereto, itbeingapmanyother specific formulations pare t. ha may be prepared which would fall within--the teaching of-our invention.

Having thus described our invention, we claim:

1. A flux composition for treating aluminum and aluminum base metal alloys comprising 30 to 70% of an alkali metal fluoborate, 30 to 70% of an alkali metal fluotitanate and to 40% of sodium chloride.

2. A flux composition for treating aluminum and aluminum base metal alloys comprising 80 to 70% of an alkali metal fluoborate, 30 to 70% of an alkali metal fluotitanate and 10 to 40% of cryolite.

3. A flux composition for treating aluminum and aluminum base metal alloys comprising 30 to 70% of an alkali metal fluoborate, 30 to 70% of an alkali metal fluotitanate and 10 to 40% of calcium fluoride, at least one of said alkali metals being sodium.

4. A method of improving the characteristics of aluminum and aluminum base metal alloys, including heat treatable alloys, comprising maintaining said aluminum and aluminum alloy in a molten state, and inserting within the body of said molten aluminum and aluminum alloy a treating mixture comprising an alkali metal fluoborate and an alkali metal fluotitanate, the alkali metal of at least one of said compounds being sodium, said combined alkali metal fluoborate and alkali metal fluotitanate being used in an amount of at least 0.1% by Weight of the Weight of the metal being treated.

5. A method of improving the characteristics of aluminum and aluminum-containing metals comprising maintaining said aluminum and aluminum-containing metals in a molten state While treating said metals with an intimate mixture of heat bonded ingredients comprising 25 to 75% of an alkali metal fluoborate and 25 to 75% of an alkali metal fiuotitanate, at least one of said alkali metals being sodium, said combined alkali metal fluoborate and alkali metal fluotitanate being used in an amount of at least 0.1% by Weight of the Weight of the metal being treated.

6. A method of treating aluminum and aluminum base metals comprising melting said metal and inserting into the body of said molten metal and near the bottom thereof a compact fused mass of fluxing material containing 25 6 to of an alkali fluoborate and 25 to 75% of an alkali fluotitanate at least one of said alkali metals being sodium, said combined alkali metal fluoborate and alkali metal fiuotitanate being used in an amount of at least 0.1% by Weight of the Weight of the metal being treated.

7. A flux composition comprising 25 to 75% of an alkali metal fluoborate, 25 to 75% of an alkali metal fiuotitanate, at least one of said alkali metals being sodium, and substantially the remainder of said composition being made up of at least one material of the group consisting of sodium chloride, sodium fluoride, calcium fluoride, sodium aluminum fluoride and magnesium fluoride.

8. The composition of claim 7 in which said alkali metal fluoborate and alkali metal fluotitanate are substantially anhydrous and are bonded together through the application of heat.

9. A flux composition comprising 25 to 75% of an alkali metal fluoborate and 25 to 75% of an alkali metal fluotitanate, at least one of said alkali metals being sodium.

10. A flux package for aluminum and aluminum base metal alloys comprising a compact fused mass containing 25 to 75% of an alkali metal fluoborate and 25 to 75% of an alkali metal fluotitanate, at least one of said alkali metals being soduim.

JAMES A. DAVIS. LA VERNE W. EASTWOOD.

References Cited in the file of this patent UNITED STATES PATENTS OTHER 4 REFERENCES "American Foundryman, April 1947, page 123. 

4. A METHOD OF IMPROVING THE CHARACTERISTICS OF ALUMINUM AND ALUMINUM BASE METAL ALLOYS, INCLUDING HEAT - TREATABLE ALLOYS, COMPRISING MAINTAINING SAID ALUMINUM AND ALUMINUM ALLOY IN A MOLTEN STATE, AND INSERTING WITHIN THE BODY OF SAID MOLTEN ALUMINUM AND ALUMINUM ALLOY A TREATING MIXTURE COMPRISING AN ALKALI METAL FLUOBORATE AND AN ALKALI METAL FLUOTITANATE, THE ALKALI METAL OF AT LEAST ONE OF SAID COMPONENTS BEING SODIUM, SAID COMBINED ALKALI METAL FLUOBORATE AND ALKALI METAL FLUOTITANATE BEING USED IN AN AMOUNT OF AT LEAST 0.1% BY WEIGHT OF THE WEIGHT OF THE METAL BEING TREATED. 